Pre-recorded or self-recorded optical discs may support “Out Of Multiplex” (OOM) formats. Out of multiplex is a format that stores different streaming components, e.g. video, audio and subtitles, on different locations on the disc, i.e. different files. This is possible with various standardized media, e.g. Blu-ray disc or DVD. Also, a video technique known as multi-angle may be implemented. Multi-angle means that a video film may contain for certain scenes various alternative view angles, all running at a parallel time axis, which are selectable by the user and may be integrated seamlessly into the video.
To playback an OOM source, the optical pick-up reads all required streams from the different locations, before the playback device decodes the streams by their specific decoders for synchronous representation. That means that the pick-up has to jump from stream to stream in order to serve all decoders simultaneously, without noticeable interruption of the presentation. Usually, a pick-up contains an actuator carrying an optical sensor, and the pick-up is movable by a mechanical drive for raw adjustment, while the actuator is separately movable for fine adjustment without a mechanical drive.
The straight forward solution for providing OOM technology with optical drives is buffer technique: additional stream buffers 61, 62, 63 serve to bridge the times that are needed for jumping to the other requested streams and reading them 53. A typical example comprises three streams: video, audio and subtitles. E.g. the video buffer is dimensioned such that jumping to the audio stream, loading of the audio buffer, jumping to the subtitle stream, loading of the subtitle buffer and jumping back to the video stream can be executed without the video buffer running empty. The other buffers, e.g. for audio and subtitles, are dimensioned analogously.